Ring Transformation of Cyclopropenes to Benzo-Fused Five-Membered Oxa- and Aza-Heterocycles via a Formal [4+1] Cyclization.

In the context of the growing importance of heterocyclic compounds across various disciplines, numerous strategies for their construction have emerged. Exploiting the distinctive properties of cyclopropenes, this study introduces an innovative approach for the synthesis of benzo-fused five-membered oxa- and aza-heterocycles through a formal [4+1] cyclization and subsequent acid-catalyzed intramolecular O- to N- rearrangement. These transformations exhibit mild reaction conditions and a wide substrate scope. The applications in the late-stage modification of complex molecules and in the synthesis of a potential PD-L1 gene down-regulator, make this method highly appealing in related fields. Combined experimental mechanistic studies and DFT calculations demonstrate Rh(III)-mediated sequential C─H coupling/π-allylation/dynamically favorable O-attack route.

Generation of concentric perfect Poincaré beams.

We theoretically propose and experimentally verify a method to generate new polycyclic beams, namely concentric perfect Poincaré beams (CPPBs), by using an encoded annular phase mask. The proposed beams consisting of multiple polarization structured fields can be simultaneously generated in one concentric mode, which are respectively mapped by fundamental Poincaré sphere (PS), high-order Poincaré sphere (HOPS), and hybrid-order Poincaré sphere (HyPS). Moreover, the ring radius, numbers and polarization orders of the CPPBs at arbitrary positions on arbitrary PS are independently controlled. This work enriches the mode distributions of perfect vortex and introduces a new polarization degree of freedom, which has the potential to implement more information beyond the orbital angular momentum multiplexing in optical communication.